Bridge-type hardness tester



' Filed July 15, 1946 June 14, 1949.

D. F. SKLAR 2,473,179

BRIDGE-TYPE HARDNESS TESTER 3 Sheets-Shee i INVENTOR ATTORNEY June 14, 1949.' D. F. SKLAR BRIDGE-TYPE HARDNESS TESTER 3 Sheeis-Sheet 2 Filed July 15;, 1946 INVENTOR Dav/u E 5x441? ATTORNEY June 14, 1949. D. F..SKLAR BRIDGE-TYPE HARDNESS TESTER 3 Sheets-Sheet 3 Filed July 15, 1946 INVENTOR Dav/p S/MAR BY I 2 ATTORNEY Patented June 14, 1949 BRlDGEi-aTY'PEl HARDiNESS TESTER David F. Sklar, Brookly N. Y., assignor to- Wilson Mechanical Instrument 20., 11.10., New York, N. Y., a corporation of New York Application July: 15, 1946,. SerialNoa. 683,610

20" Claims. (CI. 73-83.)

This. invention relates to machines. for testing the-hardness of metals or like materials and. more particularly to machines for testing the hard ness. of large or heavy articles, or structures or parts thereof that could not. be easily handled by the type of hardness testing machines having movable test piece supports; though it is noted that in some of the claims the invention is not limited to machines for testing heavy or bulky articles.

One object of the invention is .to provide an improved testing machine of this kind which. is particularly adaptable to be mounted over a part of a separately supported large machine or structure, accommodating the testing machine to the structure of which the hardness is to be tested rather than moving or accommodating. Said structure tothe testing machine.

Other objects of the invention are to. provide in an improved machine of this. kind, means for preventing objectionable lost. motion or; ,looseness between parts of the machine, and to provide a means for dust-proofing parts-- and to. provide a machine which may be conveniently secured to a. supporting structure over the part-tube tested.

Additional objects of. the invention are to efiect simplicity and efficiency in such machines and to: provide: anextremely simple: machine of: this kind. which is accurate, reliable and durable in operation, and economical to manufacture and install.

Still other objects of the invention will appear as the description proceeds; and while herein details of the invention are described in-v the spec ification and some of the claims, the invention as described in the broader claims is not limited to these, and many and various changes may be I made without departing from the scope of the invention as claimed in the broader. claims.

The inventive features for the accomplishment of these and other objects are shown hereinin connection with a hardness testing machine which briefly stated, includes a horizontal elongated fixed bridge adapted to be supported above a test piece and having upper bearing. bores there.- in and carrying housings secured fast on the bridge having removable front walls, lower bearing openings, the bores and openings respectively receiving bushings receiving pending screws carrying a lower movable bridge fast on the lower ends of the screws. An. internally threaded collar on each. screw is pressed against the upper bushings by a spring compressed between the lower bushing and the collar; and. means are.

2" provided for simultaneously rotating said. collars for raising and. lowering the movable bridge.

The. movable bridge and a rearward extension thereof carry testing mechanism comprising; a vertical plunger mounted for vertical movement on the movable bridgeandcarrying a penetrator point, below the bridge, meansbeing: provided for applying a. minor load to the plunger as the bridge is lowered. and for subsequently applying a major load to the plunger to. effect penetrationto. operate. a. gauge. operatively connected to the. plunger.

In the accompanying. drawing showing, by way of, example, one of many, possible embodiments of the invention,

Fig. 1 is a front elevation of the machin mounted on; a structure. which may be erected over a separately supported part tobe tested;

Fig. 2.is afront elevation elevation. showing the machine. mounted: on a. different tructure, one of. the housing front walls being removed. the other housing and associated parts being shown in axial. section;

I Fig.3 is a side elevationv of saidextensionand testing mechanism thereon,. partbeing shown. in vertical section; and

Figs. 4; and. 5 are respectively front elevation,

parts. being. removed. and. fragmental side elem.- tion of another form of the tester. g The various parts, of my improved hardness tester. are carried. pending from a. horizontally elongated fixed bridge l0: adapted to be secured onthelower face ofasuitable. support Ii (Fig-1.) held above a test piece I2 or to be. supported ona. frame [5,, [6 1 (Fig.. 2) including, a base. It. on which. a test piecev IZ-a issupported.

The .test. piece l2 may bea partof alarge machine too large to accommodate itself. to. the frame l5; l6, anda particular object. of the. pres:- ent inventionis to provide a. hardness tester par.- ticularly adapted. tobe secured. in, pending position. from a frame which may bedesigned and constructed by the ShQ-R. or firm using. the hard.- ness tester.

Such a frame. is. somewhat diagrammatically illustratedlin Fig. 1.. and comprises an upper support or channel beam. I! to the lower face of a %lower web. of. which said. fi'xed v bridge is secured by bolts [8,, as willbe explained- Said support or beam IT is shownv supported on two suitably supported upright channel members. l5a, angle pieces l9 being boltedto. flanges of themembers 15a. andbeam Ll to support'thelatter. Bolt. holes may, be. provided. at a y. p t al n said flanges to accommodate the frame to the particular part to. be tested.

The frame II, Ia and test piece l2 may be separately supported on the floor or ground I9, or the tester may be supported on a frame erected on the machine having the part to be tested. Any other suitable supporting structure may be used.

The fixed bridge has vertical end bores in its opposite ends in which are received the bolts I8 (Fig. 1) or the reduced upper end-s 2| of the columns I5 of the frame I5, I6, the lower ends being similarly held fast on the elongated flat base I6 adapted to receive the test piece I2 thereon.

Said bridge I 9 has intermediate axially vertical upper bearing bores 22 (Fig. 2) near said end bores, and lower rectangular bosses 23 surrounding the bearing bores and receiving housings 25 secured fast to the lower face of the bridge, having removable front walls 25a (Fig. 3). Each housing has an open upper end received on the associated boss, and a lower wall 26 having a lower bearing opening 21 therein in vertical alinement with the upper bearing bore. Intermediately flanged upper and lower bearing bushings 29, 30 are disposed in said bearing bore and opening respectively, the flanges 3|, 32 thereof engaging against the boss and lower wall respectively. An undercut collar 33 mounted fast on the lower face of the boss 23 around the associated bushing has an inner flange engaged under the flange 32 to hold the upper bushing in the bore.

Operating screws 35 are vertically slidable on the bushings and each receives thereon an internally threaded collar 35 engaged with the upper bushing and having an intermediate flange 3? and a reduced diameter lower portion 38. A bearing washer 39 engages on the lower face of the collar flange and has a lower reduced diameter portion 49, and an inner rabbet groove 4i receiving said reduced portion 38 of the collar to hold the washer spaced from the screw. A thrust washer 42 engaged against the lower face of the bearing washer has an upper inner groove 43 receiving the reduced portion of the bearing washer, and has a lower reduced diameter portion 44. A strong helical spring 45 compressed between the thrust washer 42 and the flange 32 of the lower bushing receives the reduced diameter portions 4?, 44 of said bushing 39 and thrust washer 42 to hold the threaded collar 3'! firmly seated against the upper bearing bushing 29.

Worm wheels mounted fast on collars 36 and the upper face of the flange 31 thereof are engaged by worms 5| fast on a worm shaft 52 rotary in alined pairs of alined bearings 53 set in opposite walls of the housings 25 respectively. A counterbalanced crank 54 is mounted fast on one end of said shaft, whereby said shaft, worms and worm wheels may be rotated to lower or raise the operating screws 35.

Inverted telescoping cups 55 are mounted over the ends of the operating screws 35 respectively to prevent access to the screws of dust or other foreign matter. Each cup comprises an intermediate section 56, a lower section 51 secured fast to the upper bushing 39, and upper section 58 having an upper end wall 59.

A movable bridge 60 has end bores 62 received and held fast on reduced lower portions 63 of the screws, whereby the bridge 60 is lowered and raised when th screws 35 are lowered and raised.

The helical springs 45 are quite strong and are amply strong enough to overcome the weight the spindle 95.

4 of the bridge 60 and all parts supported thereon thereby to hold the collar 36 firmly against the bushing 29 to prevent any lost motion between the collar, bushing or bridge l0.

Said movable bridge has at its mid-part a central axially vertical bore 54 and a rear supporting extension 55 (Fig. 3) perpendicular to the bridge and supporting a testing mechanism about to be described including a base 66 fast on said bridge and extension and having a bore 67 coaxial with the central bore 64, and spaced side walls 68, 69 provided with spaced front standards I9 and spaced rear standards 'I I. A plunger sleeve I3, I4 having a large lower portion I3 in said central bore 64 and a threaded reduced diameter portion 74 fitted in the bore 61 of said base, carries a nut '15 on said threaded portion engaging said bas and holding the sleeve in place. Said sleeve has a bore I5 therethrough having a reduced diameter lower portion 'I'I forming an intermediate upwardly facing conical seat IS. A plunger I9 in said sleeve of the bridge and having an intermediate cylindrical portion 89 has a lower conical face 8| resting on said seat, a lower reduced diameter portion 82 in the lower part of the sleeve carrying a penetrator 83 at the lower end, and an upper loading rod 84 coaxial with the sleeve and extending to near the top of the front standards ID.

A helical minor load spring 99 around the rod rests on said cylindrical portion 89; and a seating collar 9| slidably received on the rod rests on the spring. A tubular double knife edge member 92 on the rod has its lower knife edge 93 resting on the seating collar; and a major load power lever 94 between said side walls 68, 69 has knife edges 95 fulcrumed on said standards 10 a short distance from the member 92, the lever resting on the upper knife edge 95 of the member 92 and having its rear free end 91 projecting beyond the base and carrying a major load weight 98.

A control lever I09 fulcrumed between said rear standards 'EI and extending to near the front standards is laterally offset (frontwardly offset in Fig. 3) at its forward free end I0! which is provided with a transverse pin I02. The lever I99 is provided intermediately near its fulcrum end with a link I93 carrying a lateral pin I04 engaging in an opening in the power lever 94 for raising and lowering the latter.

A rotary spindle I95 (Figs. 2 and 3) transversely mounted in said side walls 68, 69 to the rear of the front standard is provided with an outer and crank I96 and at the inner end with a trip arm IJl engaging against said transverse pin 592 of the control lever I99 to hold the latter and the power lever raised until forward movement of the crank it causes the trip arm to release the control lever and allow the control lever to move downwardly. A toggle link I98 pivoted on said transverse pin Hi2 and an intermediate part ofthe trip lever I ll? serves for raising the control lever on reverse rotation of A dash-pot [I9 mounted on the side wall 68 has its piston rod connected to the control lever for preventing sudden dropping of said levers 94 and hit.

housing H6 secured by screws II! to the side 5 walls 69 covers said wall's' tfl, 69, standards Til, H and levers 94, Hill.

The bridges l and it and the extensions 65 may be hollowed out and provided with inner strengthening ribs I20, l2! and I22 respectively, if desired.

The operation of the tester will be readily understood and need be only summarized as follows:

The piece 12, 12a to be tested may be placed under the penetrator or the tester may be placed over the part to be tested. Then the handle 54 is turned to gently lower the bridge '69 until the penetrator 83 comes into contact with the test piece. The turning of the crank c is continued slowly until the plunger 19 compresses the minor load spring 90 sufficiently to apply the minor load.

The major load may then be'applied by pressing the crank handle It? forwardly to release the trip arm [M from the pin Hi2. This allows the lowering of the levers M and Hi0 and applies the major load uniformly to the penetrating point 83, forcing it into the test piece to a depth depending upon its hardness. The major load is then removed before taking the hardness number from the dial. This is done by turning the crank handle rearwardly causing the trip lever I01 and link I03 to act as a toggle raising the lever I00 and. bringing the end of the trip lever l0! under the pin I02 to hold the levers 94 and )0 and the penetrator raised, after which the reading may be taken from the dial.

While two operating screws 35 are shown in Figs. 1 to 3, I may wish to use a single centrally located screw 35a as shown in Figs. 4 and 5, in which the construction and operation of the tester is similar to that of the tester of Figs. 1 to 3, except as now noted.

Only one housing is required and consequently the stationary bridge member Illa and the shaft 52a are made short.

The single operating screw of Figs. 4 and 5 is provided with a longitudinal groove b receiving a lug 3% fast in the lower bushing 39a, which is held fast in the lower part of the housing 25. This prevents the screw from turning during operation.

The threads of the screw 35a extend to the lower end of the screw and are received fast in a threaded bore I25 of a block secured by corner screws 12'! engaging in upwardly extending front standards 100., similar to but taller than the standards ll] of Figs. 2 and 3. The upper inner edge portion of the standards 10a are rabbeted as at I28 to receive a similar rabbeted portion at the lower face of the block I26 to cooperate with the screws to hold the latter firmly in place.

The lower support a is only as wide as is necessary to support the bore 66, as shown in Fig. 4. The housing Ilfia is cut away as at 6b to receive the block I26.

The operation of the tester of Figs. 4 and 5 is thesame as that of Figs. 1 to 3.

The invention claimed is:

1. In combination, a horizontally elongated member adapted to be fixedly supported above a test piece and having axially vertical bearings therein; pending screws slidable in the bearings and extending below the bearings and member; an internally threaded rotary collar on each screw in threaded engagement with the screw; means holding said. collar against upward or downward movement relative to the member; means for rotating the collars; a movable bridge .6 supported on the lower ends of the screws; 9. downwardly pointed penetrator vertically movably mounted on the movable bridge; and means for applying a testing force to the penetrator.

2. In combination, a stationary member adapted to be fixedly supported above a test piece and having an axially vertical bearing therein; a screw slidable in the bearing and extending below the bearing and member; an internally threaded collar on the screw in threaded engagement with the screw; means holding said collar against vertical movement; means for rotating the collar; a movable member fast on the lower end of the screw; a vertically movable penetrator mounted on the movable member; and means for applying a test load to the penetrator.

' 3. In combination, a penetrator support; a penetrator thereon; operating means for effecting relative approach of said support and a test piece; load means urging the penetrator toward the test piece; said operating means comprising a member disposable above the test piece and having a bearing therein; a substantially vertical screw slidable in the bearing and carrying said penetrator support at its lower end; an internally threaded collar on the screw in threaded engagement with the screw below the bearing; spring means pressing the collar against the bearing; and means for rotating the collar.

4. In combination, a stationary member adapted to be fixedly supported above a test piece and having a vertical bearing therein; a pending screw-slidable in the bearing and extending below the bearing and member; an internally threaded collar on the screw in threaded engagement with the screw; means for rotating the collar; spring means pressing the collar upwardly against the bearing; a movable member fast on the lower end of the screw; a penetrator vertically movably mounted on the movable lower member; and means for applying a testing load to the penetrator.

5. In combination, a fixed bridge adapted to be fixedly supported above a test piece and having vertical bearings therein; pending screws slidable in the bearings and extending below the bearings and bridge; an internally threaded collar on each screw in threaded engagement with the screw; means for simultaneously rotating the collars; spring means pressing the collars upwardly against the bearings; a movable bridge fast on the lower ends of the screws; a plunger vertically movably mounted on the movable bridge and carrying a lower penetrator; and means for applying a testing load to the plunger.

6. In combination, a horizontally elongated fixed bridge adapted to be supported above a test piece and having upper bearing bores therein; housings secured fast on the bridge having lower bearing openings below said bores; bushings secured in said bearing bores and openings respectively; screws slidable in the bushings; an internally threaded collar on each screw against the upper bushing; a spring compressed between the lower' bushing and the collar; means for simultaneously rotating said collars; a movable bridge fast on the lower ends of the screws; a vertically movable plunger mounted on the movable bridge and carrying a lower downwardly pointed penetrator; and means for applying a testing load to the plunger.

'7. In combination, a fixed horizontal bridge having vertical end bores in its opposite ends, whereby the bridge may be fixedly secured to the lower face of a supporting beam fixedly suplower bearing bushings in said bearing bores respectively, the flanges thereof engaging against said boss and lower wall respectively; screws slidable in the bushings; an internally threaded collar on each screw against the upper bushing; a spring compressed between the lower bushing and the collar; means for simultaneously rotating said collars; a movable bridge fast on the lower ends of the screws; a vertically movable plunger mounted on the movable bridge and carrying a lower downwardly pointed penetrator; and means for applying a testing load to the plunger.

8. In combination, a horizontally elongated fixed bridge adapted to be supported above a test piece and having upper bearing bores therein; housings secured fast on the bridge and having lower bearing openings; bushings secured in said bearing bores and openings respectively; screws slidable in the bushings; an internally threaded collar received on each screw and engaged with the upper bushing and having an intermediate flange and a reduced diameter lower portion; a bearing washer engaged on the lower face of the collar flange and having a lower reduced diameter portion, and inner rabbet groove receiving said reduced portion of the collar to hold the washer spaced from the screw; a thrust washer engaged against the lower face of the bearing washer and having an upper inner groove receiving the reduced portion of the bearing washer, and having a lower reduced diameter portion; a strong helical spring compressed between the thrust washer and the lower bushing and receiving the reduced diameter portion of said thrust washer; a movable bridge fast on the lower ends of the screws; a plunger vertically movably mounted on the movable bridge and carrying a lower penetrator; and means for applying a testing load to the plunger.

9. In combination, a fixed bridge adapted to be fixedly supported above a test piece and having vertical bearings therein; pending screws slidable in the bearings and extending below the bearings and bridge; an internally threaded worm wheel on each screw in threaded engagement with the screw; a rotary shaft mounted tangentially of the wheels and carrying worms for simultaneously rotating the wheels; means holding the wheels against upward or downward movement; a movable bridge fast on the lower ends of the screws; a plunger vertically movably mounted on the movable bridge and carrying a lower penetrator; and means for applying a testing load to the plunger.

10. In combination, a horizontally elongated fixed bridge adapted to be supported above a test piece and having lower bosses and upper bearing bores therein; housings secured fast on the said bosses and having lower bearing openings; bushings secured in said bearing bores and openings respectively and having intermediate flanges; an undercut collar mounted fast on the lower face of the boss around the associated bushing and having an inner flange engaged under the flange of the bushing to hold the bushing in the bore; screws slidable in the bushings; an

internally threaded collar on each screw against the upper bushing; a worm wheel mounted fast on each collar and the upper face thereof; alined pairs of alined bearings set in opposite walls of the housings respectively; a worm shaft carried in said alined bearings and carrying fast thereon worms engaging said worm wheels respectively; a counterbalanced crank fast on one end of said shaft whereby said shaft, worms and worm wheels may be rotated to lower and raise the operating screws; a movable bridge fast on the lower ends of the screws; a vertically movable plunger mounted on the movable bridge and carrying a lower downwardly pointed penetrator; and means for applying a testing load to the plunger.

11. In combination, a stationary member adapted to be fixedly supported above a test piece and having an axially vertical bearing therein; a screw slidable in the bearing and extending below the bearing and member; an internally threaded collar on the screw in threaded engagement with the screw and held against vertical movement; means for rotating the collar; a movable member fast on the lower end of the screw; a vertically movable penetrator mounted on the movable member; means for applying a testing load to the penetrator; and a telescoping cup disposed over the upper end of the screw.

12. In combination, a fixed bridge adapted to be fixedly supported above a test piece and having vertical bearing openings having bearing bushings therein; pending screws slidable in the bushings and extending below the bushings and bridge; an internally threaded collar on each screw below the bushing in threaded engagement with the screw; means for holdin said collar against the bushings; means for simultaneously rotating the collars; a movable bridge fast on the lower ends of the screws; a plunger vertically movably mounted on the movable bridge and carrying a lower penetrator; means for applying a testing load to the plunger; and inverted telescoping cups mounted over the ends of the operating screws respectively, each comprising an intermediate section, a lower section mounted on the bushing, and an upper section having an upper end wall.

13. In combination, a pair of suitably supported upright channel members having holes in a flange thereof a horizontal channel beam having holes in its flanges and having its web disposed against the upper part of the webs of said members; angle pieces disposed against adjacent flanges of the beam and members; bolts passing through said holes and pieces to hold the beam and members together; a fixed bridge having end bores; bolts passing through the end bores and the lower flange of the beam for fixedly supporting the fixed bridge above a test piece disposed between said members; said bridge having vertical bearings therein; pending screws slidable in the bearings and extending below the bearings and bridge; an internally threaded collar on each screw below the collar in threaded engagement with the screw; means holding said collars against the bearings; means for rotating the collars; a movable bridge fast on the lower ends of the screws; a plunger vertically movably mounted on the movable bridge and carrying a lower penetrator; and means for applying a testing load to the plunger.

14. In combination, an elongated flat base adapted to receive a test piece thereon; upright columns mounted fast on the base near opposite ends thereof and having reduced upper ends; a horizontally elongated fixed bridge having vertical end bores received fast on said ends, said bridge having axially vertical bearings therein; pending screws slidable in the bearings and extending below the bearings and bridge; an internally threaded collar on each screw in threaded engagement with the screw, means for simultaneously rotating the collars; spring means pressing the collar upwardly against the bearings; a movable bridge fast on the lower ends of the screws; a plunger vertically movably mounted on the movable bridge and carrying a lower penetrator; and means for applying a testing load to the plunger.

15. In combination, a fixed bridge adapted to be supported above a test piece and having vertical bearings therein; pending screws slidable in the bearings and extending below the bearings and bridge and having reduced lower ends; an internally threaded collar on each screw in threaded engagement with the screw; means for supporting the collar on the bridge; means for rotating the collars; a movable bridge having end bores received and held fast on said reduced lower ends of the screws and having at its mid-part a central axially vertical bore and a rear extension perpendicular to the bridge; a base fast on said bridge and extension; and testing mechanism mounted on said base and extension and including a vertically movable plunger having a downwardly pointed penetrator below the movable bridge.

16. In combination, a member adapted to be supported above a test piece; a movable bridge having at its mid-part a central axially vertical bore and a rear extension perpendicular to the bridge; means entirely supported by said member for supporting the bridge on and below said member and raising and lowering the bridge; a base fast on said bridge and extension and having spaced front and rear standards; a plunger mounted for vertical movement in said central bore and havin a penetrator below the bridge; a minor load spring engaging and pressing on the plunger; a major load power lever fulcrumed on said front standards adapted to press on the plunger; means including a lever fulcrumed on the rear standard and connected to power lever for raising and lowering the power lever; a dial gauge operatively connected to said plunger.

17. In combination, a stationary member adapted to be disposed above a part to be tested of a large m'achine; structure for supporting said member independently of such machine adapted to be entirely laterally ofiset from said large machine while supporting the member above said part to be tested; a movable member; means entirely supported and carried by the stationary member for supporting the movable member on and below the stationary member and. gradually lowerin the movable member relatively to the stationary member; a downwardly pointed substantially vertically movable penetrator carried on the movable member and projecting below said means and movable member; and means for applying a testing load to the penetrator.

18. In combination, a stationary member adapted to be disposed above a part to be tested of a large machine and having parts adapted to be attached to structure for supporting the member and having supporting parts adapted to be entirely laterally ofiset and independent of said large machine for supporting said structure when supporting the member above said part to be tested; a movable member; movable means entirely supported and carried by the stationary member for supporting the movable member on and below the stationary member and gradually lowering the movable member relatively to the stationary member and said part to be tested; a downwardly pointed downwardly movable penetrator carried on the movable member and projecting below said means and movable member and adapted to be engaged with said part to be tested; and means for applying a testing load to the penetrator.

19. In combination, a stationary member adapted to be disposed above a part to be tested on a large machine; structure connected to and supporting said member, when so disposed, and adapted to be entirely laterally offset from said large machine and supported independently of the machine while supporting said member above said part to be tested; a movable member; means entirely supported and carried by the stationary member for supporting the movable member on and below the stationary member and gradually lowering the movable member relatively to the stationary member and said part to be tested; a downwardly pointed downwardly movable penetrator carried on the movable member and projecting below said means and movable member and adapted to be engaged with said part to be tested; and means for applying a testing load to the penetrator.

0. In combination, a horizontally elongated stationary member adapted to be disposed above a part to be tested of a large machine and having intermediately therein a pair of substantially axially vertical bearings, and having parts adapted to be attached to structure for supporting the member and having supporting parts remote from said bearings and adapted to be entirely laterally offset from and independently of said large machine for supporting said structure when supporting said member above said part to be tested; pending screws slidable in the bearings; an internally threaded rotary collar on each screw; means holding the collar against upward or downward movement relative to the member; means for rotating the collars; a movable bridge supported fast on the lower ends of the screws; a downwardly pointed penetrator downwardly movably mounted on the movable bridge and adapted to be engaged with said part to be tested; and means for applying a testing load to' the penetrator.

DAVID F. SKLAR.

REFERENCES CITED The following referenlces are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 934,776 Vosper Sept. 21, 1909 989,471 Abraham Apr. 11, 1911 1,477,851 Root Dec. 18, 1923 1,516,208 Rockwell Nov. 18, 1924 1,762,498 Wilson June 10, 1930 1,885,972 Wilson Nov. 1, 1932 1,993,103 Labarre Mar. 5, 1935 2,297,778 Knerr et a1 Oct. 6, 1942 2,385,958 Woxen Oct. 2, 1945 FOREIGN PATENTS Number Country Date 81,378 Sweden Sept. 4, 1934 

